Monoshaft propeller water-jet

ABSTRACT

A marine propulsion system providing a semisubmerged supercavitating propeller rotating coaxially with water jetproducing impellers mounted on the same shaft.

United States Patent cm E. Shields 1013 Fireside Lane, Virginia Beach, Va. 23462 July 29, 1969 Aug. 10, 1971 Inventor Appl. No. Filed Patented MONOSHAFT PROPELLER WATER-JET 3 Claims,1 Drawing Fig.

Int. Cl. B6311 11/02 Fieldolsearda l15/12,14,

Primary Examiner-Trygve M. Blix Attorneys-L. A. Miller, Q. E. Hodges and A. Sopp ABSTRACT: A marine propulsion system providing a semisubmerged supercavitating propeller rotating coaxially with water jet-producing impellers mounted on the same shaft.

47 I" n T I 5: 1 L

L'- :5; f M i MONOSHAFT PROPELLER WATER-JET The invention described herein may be manufactured and used by or for the Government of the United States of America for. governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION Conventional marine propulsion hardware has been difficult to employ successfully in high speed vessels such as surface effect ships utilizing the principle of ground effect. Supercavitating semisubmerged propellers by themselves are relatively inefficient at low speeds while water jets are rather inefficient at high speeds. Other propulsion means such as gas turbines, fan jets, turbojets, turboprops and the like are not particularly suitable at low speeds, while fully submerged propellers are relatively inefficient for high speeds. The problem has been to provide marine propulsion for high speed vessels in which propulsion efficiency is acceptable at all speeds.

SUMMARY OF THE INVENTION In solving the above-mentioned problem, there is provided according to a preferred embodiment of the present it vention a composite propulsion system of unique design en ploying both a water jet and a semisubmerged, superczvitating propeller. The impellers for the waterjet and the propeller are mounted on the same shaft and rotate in unison. Consequently, some thrust is obtained from both the water jet and propeller at all speeds, the water jet being more efficient at lower speeds and the propeller being more efi'icient at higher speeds.

More particularly, a water intake is mounted near the aft end of the underbody of the hull. A slightly curved conduit feeds the water to an axial flow impeller stage. TIlt power shaft is brought into the conduit from a forward located power plant. The conduit extends aftwardly and exits thru the transom along with the shaft. The conduit has a rotatable portionjust aft of the transom, the rotation being afforded by an additional axial flow impeller coupling the shaft to the conduit portion. The semisubmerged propeller has its blades 2 ttached to the rotating conduit portion which thus acts as the p ropeller hub. The conduit extends aftwardly of the hub in the form of an exhaust nozzle for the water jet.

By the present novel arrangement the propulsion system need not require any gearing or other loss-producing linkage between power plant and thrusters. Further, only a minimum of transverse space of the craft is needed because the tandem relation of the impeller/propeller stages on the same shaft enables longitudinal placement of the elements of the propulsion system. Because transverse space is limited in most surface effect ship designs, as well as in other high speed surfa :e craft such as hydrofoils and hydroplanes, etc., which may employ the present invention, the tandem arrangement of pow :r plant and multiple thrusters is advantageous.

OBJECTS OF THE INVENTION Accordingly, among the objects of the present inve ntion is to provide for a surface-going watercraft:

A composite thruster marine propulsion unit operalile by a single power shaft; a composite marine propulsion system employing a semisubmerged propeller and a water jet coaxial therewith having axial flow impellers for producing a aterjet and a propeller rotatable coaxially therewith to produce combined water jet and propeller thrust simultaneously; a marine propulsion unit composed of tandem mounted propeller and water jet thruster stages producing coaxial thrust from a single, common power output shaft wherein the overall efficiency of the thruster units is at least adequate at all operational speeds of the watercraft.

BRIEF DESCRIPTION OF THE DRAWINGS Reference is now made to the drawings in which-the single FIGURE is a side view of a preferred embodiment of the propulsion unit according to the invention.

DETAILED DESCRIPTION AND OPERATION OF THE INVENTION Referring to the sole figure, the propulsion system of the invention is shown mounted in the stern section of a watercraft l1 represented by a transom l3 and stern underbody 15. The stem section may be the afterbody of one of two sidewalls of a captured air bubble (CAB) vehicle, the afterbody of a planing craft, the afterbody of a hydrofoil craft, etc. There is no limitation intended as to the particular type of watercraft carrying the propulsion unit of the present invention although the propulsion unit is primarily intended for high speed watercraft capable of speeds up to about knots.

The power plant for the craft 11 is represented by the numeral 17 and is located generally forward of the stern section and having a single output shaft 19 extending aftwardly.

The propulsion unit of the invention is composed of an axial flow impeller unit 21 and a propeller unit 23 employing one or more propellers of the semisubmerged supercavitating type both the impeller unit and the propellers being mounted on the shaft 19. The impeller unit 21 is mounted in a generally fore-and-aft oriented conduit 25 having a generally upward directed inlet 27 flush mounted in a surface of the underbody 15. The conduit 25 has an aftward curving generally cylindrical wall portion 29 affording at its forward facing wall portion an opening 31 accommodating entry of the shaft 19. The shaft 19 is supported by bearings 33 at the opening 19.

The impeller stage 21 has impellers 35 and 37 mounted on a hub portion 38 of the shaft 19 for rotation therewith. The impellers are located in the conduit 25 aft of the intake 27 downstream of incoming sea water and are mounted in bearings 39 which are supported by faired radial vanes extending from the bearing to supports 41.

The shaft 19 and conduit 25 extend aftward from the impeller stage thru the transom to a further axial flow impeller stage 43. In impeller stage 43 impeller blades 45 are attached to the hub portion 38 and at their radially outward ends to an annular hubbed semisubmerged propeller 49. The blades 45 thus act as radial supports for the rotating hub 47, and the hub 47, being annular also acts as an aftward directed extension of the conduit 25. A nozzle 51 for the water jet is fixedly mounted aft of the propeller hub 47 by means of brackets 53 attached to the transom 13. Alternatively, the nozzle 51 may be a rotating extension of the hub 47. With the fixed mounting arrangement, the forward end of nozzle 51 may act as a bearing for the hub 47 and thus as a bearing for the aft portion of the shaft 19.

The operation of the invention is readily apparent from the description of the structure. Rotation of the shaft 19 by power plant 17 initiates water pumping as indicated by the arrows thru the conduit 25 and impeller stages 21 and 43 and out noz zle 51 providing water jet thrust and thus efficient low speed propulsion. The rotation of propeller 49 at low craft speeds provides some additional, though minor, thrust. As speed increases, the semisubmerged supercavitating propeller 49 produces proportionately larger thrust and makes a larger contributionto the propulsion of the craft in relation to that of the water jet since it is well known that water jets are less efficient at high speeds, say about 50 knots or more, than semisubmerged propellers.

Thus it is seen that the arrangement of the present invention provides a simple composite propulsion system in which a single shaft directly drives both the water jet and propeller thrusters to produce complementary thrusts withoutthe one appreciably dragging the other. The thrust outputs are coaxial and the overall efficiency is at least adequate at all speeds of the craft.

It is further understood that while the propulsion system has been described as being mounted at the aft end of :1 watercraft, said system maybe located at other positions of the watercraft and may be driven in reverse by simply reversing the rotational direction of the shaft.

Obviously many modifications and variations of the present invention are possible in the'light of the above teachings. lt is therefore to be understood that the invention may he practiced otherwise than as specifically described.

I claim:

1. A propulsion system for a surface or near surface watercraft comprising: 7

power plant means located in the craft;

conduit means having a rotatable portion, an inlet for receiving seawater, and an outlet;

propeller means mounted on the rotatable portion of said conduit for impacting thrust via its blades contacting the sea water externally of the conduit means;

said propeller means comprises at least one semisubmerged supercavitating propeller;

impeller means rotatably mounted within said conduit 7 means coaxial'with said propeller means; and

drive means coupled to said power plant for rotatably driving said impeller means and said propeller means via a shaft extending from the power plant into said conduit means and mounted coaxially with said propeller means and said impeller means, whereby thrust is simultaneously produced by both said propeller means and by sea water pumped by said impeller means.

2. The propulsion system according to claim 1 wherein said conduit means comprises a conduit having its inlet mounted flush on an underbody surface of the watercraft and an aftward curving portion terminating in an aftward directed conduit portion at the outlet, said rotatable conduit portion being located near the aftwardmost end of the conduit, said shaft entering said conduit at its aftward curving portion and being connected to said impeller means within the conduit and to the rotatable portion of said conduit means carrying the propeller means.

3. The propulsion system according to claim l wherein said conduit means comprises at its outlet a fixed portion, and bracket means attaching said fixed portion to the body of the watercraft. 

1. A propulsion system for a surface or near surface watercraft comprising: power plant means located in the craft; conduit means having a rotatable portion, an inlet for receiving sea water, and an outlet; propeller means mounted on the rotatable portion of said conduit for impacting thrust via its blades contacting the sea water externally of the conduit means; said propeller means comprises at least one semisubmerged supercavitating propeller; impeller means rotatably mounted within said conduit means coaxial with said propeller means; and drive means coupled to said power plant for rotatably driving said impeller means and said propeller means via a shaft extending from the power plant into said conduit means and mounted coaxially with said propeller means and said impeller means, whereby thrust is simultaneously produced by both said propeller means and by sea water pumped by said impeller means.
 2. The propulsion system according to claim 1 wherein said conduit means comprises a conduit having its inlet mounted flush on an underbody surface of the watercraft and an aftward curving portion terminating in an aftward directed conduit portion at the outlet, said rotatable conduit portion being located near the aftwardmost end of the conduit, said shaft entering said conduit at its aftward curving portion and being connected to said impeller means within the conduit and to the rotatable portion of said conduit means carrying the propeller means.
 3. The propulsion system according to claim 1 wherein said conduit means comprises at its outlet a fixed portion, and bracket means attaching said fixed portion to the body of the watercraft. 